A window blind for a motor-vehicle rear window as described in European patent 0,221,573 of E. Walter has a support, a roller rotatable in the support about a roller axis, and a motor mounted on the support and connected to the roller for rotating same about its axis. A flexible shade has one edge attached to a bar and an opposite edge attached to the roller. A pair of arms have outer ends pivoted on the bar, inner ends pivoted on the support about respective arms axes transverse to the roller axis, and central pivots so that the arms can fold in half. Respective springs provided at the central pivots urge the arms into straight positions moving the outer arm ends away from the support and stretching the shade tight between the bar and the roller.
Such a shade is deployed by rotating the roller in a direction allowing the arms to move under the force of their springs into relatively straight positions, pushing out the bar and stretching the shade between the roller and the bar. The shade is retracted by oppositely rotating the roller so that the bar is pulled in and the arms are folded under the retracted shade. Such an arrangement is fairly complex. The arms, if fully extended, must be acted on with considerable longitudinal force to fold them, at least to start with, and these arms are fairly fragile.
Similarly, European patent 0,240,747 described a similar system having a spring motor attached to the roller. This spring motor is loaded or wound up as the shade is would up so that the shade can be deployed simply by releasing the spring motor so it unwinds the shade which will then naturally be erected. This spring motor is relatively bulky, so that the complete blind system is often too big to install neatly.